Pick-resistant lock



July 20, 1965 c. A. BAUER PICK-RESISTANT LOCK Filed May 20, 1963 INVEN 1 OR ChaHes 9. Bauer RM i TTORNEYS United States Patent 3,195,330 PICK-RESHSTANT LOCK Charles A. Bauer, Woodhridge, Conm, assignor to Sargent & Company, New Haven, Conn. Filed May 20, 1963, Ser. No. 281,569 7 Claims. (Cl. -421) This invention relates to pin tumbler locks and more particularly relates to a pin tumbler lock having improved resistance and protection against picking.

Pin tumbler locks are generally constructed with a key barrel of cylindrical form which fits into a housing or body member. A bolt or locking member is operated by movement of the key barrel relative to the housing. The key barrel is normally locked to the surrounding housing by means of pins which are pressed into a locking position by biasing means, such as springs. When these pins, having distinct upper and lower portions known as drivers and tumblers are set by the proper key so that the points of contact between the drivers and tumblers coincide with the periphery of the key barrel, referred to as the shear line, the key barrel may be rotated. When a driver extends across the shear line, the barrel is locked against rotation in the housing.

and the housing, the shear line, thereby leaving the barrel free to be moved. This is usually accomplished by applying a force or torque to the key barrel and selectively raising the tumblers with a picking tool, to lift the drivers. The torque is applied to the key barrel so that once a driver is raised to its unlocking position, that is, the lower edge thereof coincides with the shear line, the key barrel can be moved sufficiently to provide a ledge upon which the raised drivers may rest to prevent the drivers from falling back into a locking position.

There has been a constant effort by lock designers to design a lock which is pick proof. However, this constant elfort on the part of lock designers seems to lag the increase in skill and determination of lock pickers. Locks may be mechanically designed so that they are extremely difficult to pick. However, such designs, for the most part, involve the provision of tumbler mechanisms and receiving wells therefor in the barrel and housing which are manufactured to very small tolerances and extremely close fits between coacting parts. The provision of such locks makes the manufactured cost of the lock extremely high, and such locks are difiicult to market because of the extremely high price.

In the past, locks which give a high degree of picking resistance, appear to be designed on the theory that the locks should be d-ifiicult to pick and yet be usable for a long period of time, even after it has been successfully picked or an attempt had been made to pick the lock. This approach, for the most part, neglects the premise that the basic purpose of the lock is to exclude,

regardless of whether a lock might be rendered inoperable, an attempted picking of the lock.

The present invention provides a new and improved pin tumbler lock providing with additional locking means which make it exceedingly diflicult to pick. Locks embodying the invention are provided with means which, upon attempted picking, permanently lock a pin across the shear line of the lock and thereby lock the barrel against movement in the housing.

An object of this invention is to provide a new and improved pin tumbler lock which is highly resistant to picking.

Another object of this invention is to provide a pin tumbler lock having new and improved security means 3,195,33h Patented July 20, 1965 "ice which prevent movement of the barrel in the lock housing it an attempt is made to pick the lock.

A further object of this invention is to provide a new and improved pin tumbler lock having security means which lock a pin across the shear line of the lock to prevent rotation of the barrel with respect to the housing if an attempt is made to pick the lock.

The features of the invention which are believed to be novel are pointed out with particularity and distinctly claimed in the claims appended to and forming part of this specification. However, the invention, both as to its organization and operation, together with further objects and advantages thereof may best be appreciated by reference to the following detailed description taken in conjunction with the drawings in which:

FIG. 1 is a side elevation, partly in section, of a cylinder of a lock embodying the invention;

FIG. 2 is a view similar to FIG. 1 showing a proper key inserted in the cylinder;

P16. 3 is a sectional view taken along line 33 of FIG. 2; and

FIG. 4 is a side elevation, similar to FIG. 1 showing a picking tool inserted in the key barrel.

A preferred embodiment of the invention comprises a lock cylinder generally indicated at 10 having a housing or body member 11 defining a generally cylindrical bore which receives a key barrel or plug 12 therein. Key barrel 12 has a bolt actuating member or roll back 13 mounted thereon, and defines a key slot 14 at least partially therethrough. In the illustrated embodiment of the invention, the lock is operated by turning key barrel 12 within the bore of lock housing 11. However, it will be understood that the invention is applicable to pin tumbler locks wherein the key barrel or equivalent plug member moves longitudinally with respect to the lock housing. As illustrated, barrel 12 is locked against rotation in housing 11 by a pin tumbler mechanism comprising a plurality of biased pin assemblies, spaced apart lengthwise of the cylinder, each of which includes a tumbler 15, a coacting driver 16 and biasing means such as a spring 17 urging coacting tumblers and drivers downwardly. Each coacting driver and tumbler and associated spring is positioned in a corresponding well 18 defined in housing 11 and a normally aligned well 18a defined in key barrel 12. The wells 18a are of greater width than key slot 14, extending through key barrel 12 as shown in FIG. 3. Springs 17, which urge the driver-tumbler assemblies int-o barrel well 18a react against a retaining plate 19 on housing 11. The tumbler-driver wells are in a parallel aligned relationship.

Each of the drivers 16 extends across the periphery of key barrel 12 between wells 18 and 18a and hence across shear line 2i). Inasmuch as each of the drivers extends across shear line 29 and normally reside in wells 18 and 18a, the drivers prevent rotation of key barrel 12 in housing 11. When a proper key is inserted into slot 14 to permit authorized operation of the lock, the key 21, by the bites thereon, lifts tumblers 15 a distance such that the points of contact of the tumblers 15 and their coacting drivers 16 are aligned at the shear line 20. The term authorized, as herein used, refers to operation of the lock by a proper key as opposed to picking of the lock. When the points of contact between tumblers 15 and drivers 16 have been aligned with the shear line 20, as illustrated in FIG. 2, key 21 may then be utilized to rotate key barrel 12 and actuate roll back 13. The structure of the lock as thus far described, is common to many pin tumbler locks.

In accordance with the invention, security means are provided for positively locking barrel 13 against movement in housing 11 if an attempt should be made to pick the lock. The security means are arranged to lock a selectedtumbler across the shear line if an attempt is made to set the driver of the selected tumbler at the shear line. Such means, in a preferred form, comprises a security plunger 22 received in a well 23 defined in barrel 12 in a direction transverse to a tumbler well 1% and in communication'therewith. One of the tumblers 24, most remote from the face of the lock, is provided with an undercut portion 25 intermediate the ends thereof. Plunger 22 is normally biased toward tumbler 24 and in engagement therewith atportion 26 thereof immediately above undercut portion 25. As shown more clearly in FIG. 1, plunger 22 normally rests against portion 26 of tumbler 24.

As shownin FIG. 2, if the tumblers, including tumbler 24 are lifted against the bias of their associated springs by a proper key 21, the point of contact with their respective drivers will coincide with shear line 20. The longitudinal dimensioning of portion 26 of tumbler 24 is 'such that when the top of tumbler 24 is raised to coincide with shear line 26, portion26 will prevent plunger 22 from being biased .into undercut portion 25. It is preferred that the dimension of the part of portion 26 "which contacts and retains plunger 22 in well 23, when in the positionshown in FIG. 2, be approximately .020". Thus, when the lock is in the normal locked position, FIG. 1, or when it is unlocked wtih a proper key, FIG. 2, tumbler 24, through portion 26 thereof, holds plunger 22in well 23.

However, should an attempt be made to pick the lock of'barrel 12 in housing 11. At this time tumbler 24 cannot be raised or lowered completely past shear line 20 due to the insertion of plunger 22 into undercut portion 25. It will be noted that this will permanently lock barrel 12 in housing 11 and thereby prevent entry through the door or other device protected by the lock. Security plunger 22 is longitudinally dimensioned such that it will not fall into the well of tumler 24 when it moves outwardly from well 23, as shown in FIG. 4.

It will be understood that security plunger 22 may be located adjacent any of the tumblers. However, for facility and simplicity of manufacture it is preferred that Well 23 and security plunger 22 therein be located adjacent th c-rearmost tumbler. Moreover, if security plun er 22 is located adjacent any but the 'rearmost tumbler, it will be noted that the key shouldnot have a high point thereon which would force the undercut tumbler above the shear line in passing thereby.

' It will be noted that if unauthorized operation of the lock is attemptedand plunger 22'is inserted into an undercut tumbler, the cylinder must'be destroyed to gain entry through the door or other device which. the lock is in- -tended to protect. While the cylinder must thus be destroyed and presents a loss, it has successfully served its purpose in preventingunauthorized entry through the door-or other'device whichit protects.

In manufacturing a lock, as exemplified in the drawings, it is preferred that the tolerance between tumbler 24, its driver and wells therefor, be made smaller thanthe tolerances of the other tumbler-driver assemblies so that the clearance or'tolerance between the periphery of tumbler 24 and its wells determines the maximum amount of play of the barrel in the housing. This arrangement would necessitate a potential lock picker to attempt to first set the driver above tumbler 24 on an edge of or, ledge provided by key barrel 12 at the shear line before attempting to set any of the other drivers at the shear line. Inasmuch as the potential lock picker is working by feel he will raise tumbler 24 above shear line 2t) and apply a torque to key barrel 12 so that key barrel 12 will provide a ledge for the driver to rest upon as the top of tumbler 24 islowered to the shear line. When tumbler '24 is raised above shear line 20 by the small predeterlock having only one driver-tumbler assembly. Various other modifications may be made tothe disclosedembodiment of the invention without departing from the spirit and scope of the invention.

Accordingly, it is intended that the appended claims cover all modifications of the disclosed invention as well as other embodiments thereof which do not depart from the spirit and scope of the invention.

What is claimed is: I

ll. Alock comprising a housing, a key barrel mounted in said housing for rotation therein and defining a shear line therewith, -a pin tumbler mechanism locking said barrel against rotation'therein comprising a plurality of coacting driver and tumbler assemblies'received in aligned wells defined by said housing and said barrel and further comprising means biasing said tumbler and driver assemsaid plunger being effective to extend into saidundercut portionif said one of said tumblers is lifted above the shear line and prevent lowering of said one of said turna locking position wherebysaid driver crosses said shear line and locks said barrel against rotation in said housing,-said tumbler being of generally cylindrical shape, said tumbler being undercut intermediate its ends, a well defined in said barrel transverse to the well receiving said undercut tumbler, and a plunger positioned in said transverse well and biased toward said tumbler well, said plunger contacting said tumbler above the undercut portion thereof and being retained in its well thereby, said plunger being eitective to extend into said undercut portion if said one of said tumblers is lifted above the shear line and prevent lowering of said tumbler below the shear line;

3. The lock of claim 2 comprising: a plurality of tumbler-driver assemblies in parallel wells,"said plunger well communicating with the tumbler Well furthcst distant from the face of the lock.

4. The lock of claim 2 wherein said plunger is forced intosa'id undercut portion if said tumbler is raised more than about .020" above said shear line.

5. The lock of claim 2 wherein the spring constant of said means biasing said tumbler and driver in a locking position is selected to prevent bouncing of said tumbler on a proper key inserted into said lock.

6. A lock comprising a housing, a key barrel mounted in said housing for rotation therein and defining a shear line therewith, a pin tumbler mechanism locking said barrel against rotation therein comprising at least one coacting driver and tumbler received in aligned wells defined by said housing and said barrel and further comprising means biasing said tumbler and driver toward a locking position whereby said driver crosses said shear line and locks said barrel against rotation in said housing, said tumbler normally lying within said well in the barrel, and security means in said key barrel extending in substantially the same longitudinal plane of the barrel as the pin tumbler mechanism, said security means including a bore formed in the back end of the barrel communicating with said well and further comprising a security member slidable in the bore and having means associated therewith to drive said member toward said well, said member and said tumbler having coacting means which, when the tumbler is lifted a predetermined distance beyond the shear line, as in picking of the lock, secure the tumbler in position to prevent rotation of said barrel.

7. A lock comprising a housing, a key barrel mounted in said housing for rotation therein and defining a shear line therewith, a pin tumbler mechanism locking said barrel against rotation therein comprising at least one coacting driver and tumbler received in aligned wells defined by said housing and said barrel and further comprising means biasing said tumbler and driver toward a locking position whereby said driver crosses said shear line and locks said barrel against rotation in said housing, said tumbler being recessed intermediate its ends, an

opening defined in said barrel transverse to the well re- References Cited by the Examiner UNITED STATES PATENTS 1,707,922 4/29 Pepper -421 2,137,504 11/38 OConnell 70364 2,836,973 6/58 Schillizzi 70-421 ALBERT H. KAMPE, Primary Examiner. 

1. A LOCK COMPRISING A HOUSING, A KEY BARREL MOUNTED IN SAID HOUSING FOR ROTATION THEREIN AND DEFINING A SHEAR LINE THEREWITH, A PIN TUMBLER MECHANISM LOCKING SAID BARREL AGAINST ROTATION THEREIN COMPRISING A PLURALITY OF COACTING DRIVER AND TUMBLER ASSEMBLIES RECEIVED IN ALIGNED WELLS DEFINED BY SAID HOUSING AND SAID BARREL AND FURTHER COMPRISING MEANS BIASING SAID TUMBLER AND DRIVER ASSEMBLIES TOWARD A LOCKING POSITION WHEREBY SAID DRIVERS CROSS SAID SHEAR LINE AND LOCK SAID BARREL AGAINST ROTATION IN SAID HOUSING, ONE OF SAID TUMBLERS BEING UNDERCUT INTERMEDIATE ITS ENDS, A WELL DEFINED IN SAID BARREL TRANSVERSE TO THE ONE OF SAID TUMBLER WELLS RECEIVING SAID UNDERCUT TUMBLER, AND A PLUNGER POSITIONED IN SAID TRANSVERSE WELL AND BIASED TOWARD SAID ONE OF SAID TUMBLER WELLS, SAID PLUNGER CONTACTING SAID ONE OF SAID TUMBLERS ABOVE THE UNDERCUT PORTION THEREOF AND BEING RETAINED IN ITS WELL THEREBY, SAID PLUNGER BEING EFFECTIVE TO EXTEND INTO SAID UNDERCUT PORTION IF SAID ONE OF SAID TUMBLERS IS LIFTED ABOVE THE SHEAR LINE AND PREVENT LOWERING OF SAID ONE OF SAID TUMBLERS BELOW THE SHEAR LINE. 